Heat-exchange apparatus



June 12, 19280 A T. W. MUNFORD HEAT EXCHANGE APPARATUS Filed April 9,1926 yvvM-mz V aw;

WI T/VAS'SES Patented June 12, 1928.

UNITED STATES PATENT OFFICE.

THEODORE W. MUNFOBD, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO MAN'I'IiEENGINEERING COMPANY, A CORPQRATION OF I'ENNSYLVANIA.

HEAT-EXCHANGE APPARATUS.

Application filed April 9, 1923. Serial No. 100,844.

This invention relates to heat exchange apparatus and more particularlyto the type used in connection, with a flue chamber or the like for thepurpose of utilizing the heat of combustion gases for the urpose ofraising the temperature of a fluid such, for example, as air passedthrough the apparatus.

Although the most-form eflicient of heat exchanger is the straightcounter flow type,

in which .the direction of flow of the fluid passing through theapparatus to be heated 1s 0 posite to the direction of flow of theheating gases, this t pe has certain practical disadvantages whic resultfrom the fact that that part of the apparatus which is exposed to thehighest temperature of the heating gases is also the part conveying thehottest fluid to be heated with the result that the temperature of thematerial from which the heat exchanger is constructed at that point maybe so high as to materially reduce the effective life of the structure.In view of the fact that the counter flow type of heat exchanger insuresthe greatest mean temperature difference between the fluid to be heatedand the heating gases, this type of apparatus takes the greatestadvantage of the convected heat but fails, on the other hand toefliciently utilize the radiant heat available from sources outside ofthe heating gases such, for example, as the brick settings of theassociated flue chamber or the like, and this is due to the fact thatsuch heat is most intense at the point where the heating fluid entersthe apparatus which, in a counter-flow type, is also the point where thefluid to be heated is hottest so that the heat transfer at this point isrelatively low, due to the fact that, as stated in Stefan- Boltzmannslaw, the rate of heat transfer by radiation from a hotter to a coolerbod is proportional to the difference in the fourt .powers of theirabsolute temperatures.

An object of this invention is to rovide a heat exchange apparatus ofsuc construction and arrangement that the flow of fluid to be heatedthrough that part of theapparatus subjected to the highest temperaturecan be given a predetermined characteristic such, for example, asquantity flow,

regardless of the total flow through theapparatus.

A further object is to provide a device of the type set forth of suchconstruction and arrangement as to obtain the utmost effect ofthe'radiant heat of the associated structure and at the same timemaintain the greatest mean temperature difference between thetemperature of the heating gases and that of the fluid to be heated soas to obtain the most .efiicient transfer of heat.

These and other objects which will be obvious to those skilled in thisparticular art are attained b means of this invention, one form of whicis illustrated in the accompanying drawing, which shows a sectional vlewthrough part of a heat exchange apparatus constructed in accordance withone embodiment of this invention.

The particular embodiment of this inventiouwhich has been chosen for thepurposes of illustration includes a fluid transmitting chamber orsection provided with an arrangement of conduits or passages throughwhich the fluid to be heated, such as air, is passed. Two passages areprovided adjacent that end of the structure which is sub jected to thehighest temperature, the bottom in the illustrated form, and thesepassages are associated in parallel relation for the transmission ofseparate streams of fluid directed thereto from separate inlets. Eachpassage leads to the same duct or manifold where the two streams areunited and through which they flow to a third passageway positioned inseries relationsh1p with the preceding passageways and from which thefluid is carried to the outlet of the apparatus. As illustrated, the twopassageways in parallel relation are so formed as to direct therespective streams of air assing therethrough in a cross paralleldirection with relation to the direction of the heating gases while thethird passageway in series with the two preceding passageways is soformed as to direct the combined streams in a cross counter flow withrelation to the heating gases. The direction of flow of the heatinbetween the assembled sections 19 indicated by the arrow A on r thedrawing. Although the drawing illustrates a. single fluid transmittingsection it will, of course, be apparent that any number of thesesectlons can be assembled with proper manifolding to provide a heatexchange apparatus of any desired size, as more fully described incopending applications, Serial Nos. 41,135 and 100,862 filed July 2,1925, and April 9, 1926, respectively.

As illustrated, each section is provided with a fluid inlet 5 associatedwith an inlet manifold 6 leading to an entrance 7 of a passageway orconduit 8 formed adjacent that end of the section which is subjected tothe highest temperature both from the flue ases and the radiant heat ofthe associated ue chamber. The air flows through the passage 8 in acircuitous route formed by suitable positioned baflles 9 and also in agenerally upward direction parallel to the flow of the heating gasesand. thence outwardly through an opening 10 into a manifold 11. A baflle12 is positioned in the manifold 11 opposite the opening 10 for thepurpose of directing the stream of air issuin therefrom into the extremeend of the manifold 11 so as to prevent the formation of a dead airpocket in the manifold between the end thereof of the outlet opening 10which would result in such a high temperature at that point as to causerapid deterioration of the material forming the apparatus.

A second inlet 13 admits a separate stream of air to a second inletmanifold 14 leading to the entrance 15 of a second passageway 16associated with the first passageway 8 in parallel relation and throughwhich the second stream of air flows in a circuitous route formed bybaflles 17 into an outlet 18 leading to the manifold 11.

The two streams of air issuing from the passages or conduits in parallelwith each other combine in the manifold 11 to form a single stream ofair which passes through an opening 19 adjacent the opposite end of theapparatus into a passageway or conduit 20 through which it flows in acircuitous route formed by baflies 21 in a direction counter to the flowof the heating gases. The stream emerges from the counter flow passage20- through an opening 22 to a manifold 23 through an outlet duct 24 atthe top of the device to an outlet 25. A valve 26 is associated witheach inlet so as to provide a. means for separately controlling the flowof the parallel streams of air admitted to the apparatus and anautomatic control for the separate streams of air can be provided asdescribed in the copending applications, above referred to, to as toobtain flexibility of operation. I

It will be apparent that either or both sets of baflles 9 and 17 in thetwo lower passages or conduits 8 and 16, respectlvely,

can be omitted so that the respective streams of air will flow acrossthe hot end of the apparatus in a straight cross current direction.-

By directin two streams of relatively cold air imme 'ately into thehottest part of the apparatus the utmost advantage is taken of theradiant heat of the flue gases and the associated flue chamberconstruction. The introduction of relatively cold fluid at this pointmaintains the material from which the apparatus is constructed at atemperature within safe limits and the most eflicient heat transfer iseffected. At the same time the provision of a counter flow chamber inseries with two cross flow chambers insures the greatest meantemperature difference between the heating gases and fluid passingthrough the ap aratus so that the utmost effect is obtained from theconvectcd heat of the flue gases.

Although I have described a specific form of heat exchange apparatus itwill be apparent that various changes, additions, omissions andsubstitutions can be made therein without departing from the spirit o.-the invention or the scope of the appendedclaims.

What I claim as new and desire to secure by Letters Patent is:

1. A heat exchange apparatus having in combination a lurality ofconduits for the passage of fluid to be heated assembled in parallelrelation for the passage of separate streams of fluid through that partof the apparatus subjected to the highest temperature and a counter flowpassage in series with said conduits for directing the fluid issuin fromeach of said conduits in a direction counter to the flow of the heatinggases.

2. A heat exchange apparatus having in combination, a conduit fordirecting a'stream of air thro h that part of the apparatus subjected tot e highest temperature, an inlet for admitting relatively cold airthereto, a second conduit adjacent said first conduit an inlet foradmitting a separate stream of relatively cold air to said secondconduit, an air duct, an outlet from each conduit thereto and a thirdconduit for directing the air from said duct through the apparatus in adirection counter to the direction of flow of the heating gases.

3. A heat exchange apparatus having in combination assages for conveyingseparate streams of uid to be heated through the hottest part of saidapparatus, means for uniting said streams and a' passage for directingsaid united streams in a direction counter to the direction of flow ofthe heat ing gases with which said apparatus is associated.

4. A heat exchaplge ap aratus having in combination a plur ty 0 passagesfor conveying separate streams of air through that a direction counterto the direction of flow of part of the apparatus subjected to thehighthe heating gases. est temperature, a duct to which said pas- Intestimony whereof, I have hereunto 1 sages lead and wherein said streamsare subscribed my name this 2nd day of April 5 united, an outlet and apassage between said 1926.

duct and said outlet for directing the united streams through a part ofsaid apparatus in THEODORE W. MUNFORD.

